Plural channel tone coloring system with common mixer for electronic musical instrument

ABSTRACT

A tone coloring system for an electronic musical instrument simulates an accordion or harmonica sound, which consists in mixing a fundamental tone signal emitted from an accurately tuned first tone generating circuit and having the tone colors of string voice or reed voice with a signal obtained from a second tone generating circuit which has a frequency difference of 3 to 10 Hz. as compared with the fundamental tone signal, a voltage corresponding to 3 to 6db. lower than that of said fundamental signal and is capable of producing the tone color of the like voice as represented by said fundamental tone signal and using these mixed signals as the musical tone signals of an electronic musical instrument to be played.

United States Patent Inventor Takeshi Adachi v Hamamatsu-shi, Japan Appl. No. 791,088 Filed Jan. 14, 1969 Patented Mar. 9, 1971 Assignce Nippon Gakki Seizo Kabushiki Kaisha l-lamamatsu-shi, Japan Priority Jan. 18, 1968 Japan 2793 PLURAL CHANNEL TONE COLORING SYSTEM WITH COMMON MIXER FOR ELECTRONIC MUSICAL INSTRUMENT 6 Claims, 5 Drawing Figs. US. Cl 84/ 1.22 Int. Cl Gl0h 106 Field of Search 84/1.11, 1.12, 1.19l.24, (B,F) References Cited UNITED STATES PATENTS 1,823,724 9/1931 Carlson 84/1 .24X

" KEYING- CIRCUIT 2,755,695 7/1956 Krauss et al. 84/1.2 2,906,157 9/1959 Peterson 84/1 .19 3,215,767 11/1965 Martin 84/1.24 3,443,463 5/1969 Campbell 34/ l .01

Primary Examiner-Milton O. l-lirshfield Assistant Examiner-Stanley J. Witkowski Attorney-Flynn & Frishauf ABSTRACT: A tone coloring system for an electronic musical instrument simulates an accordion or harmonica sound, which consists in mixing a fundamental tone signal emitted from an accurately tuned first tone generating circuit and having thetone colors of string voice or reed voice with a signal obtained from a second tone generating circuit which has a frequency difference of 3 to 10 Hz. as compared with the fundamental tone signal, a voltage corresponding to 3 to 6db. lower than that of said fundamental signal and is capable of producing the tone color of the like voice as represented by said fundamental tone signal and using these mixed signals as the musical tone signals of an electronic musical instrument to be played.

TABLET DEVI CE ouT PUT Is DEVICE TABLET MIX.

TONE COLORING 42 CIRCUIT CIRCUIT 16 SHEET 1 0F 2 TONE COLORING FIG. 20

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KEYING CIRCUIT CIRCUIT KEYING INVENTOR. BY W a 60 I25 250 560 IOOO 2600 5 AD FREQUENCY (HZ) b 0) mm 2 2 O C -wm G 0% w% F F 0 I5 i 5 9 0 6 L. I ILIIIII m 3 O 5 M. II A IV Ial Q5 072i wozwmwngo 02m30mmm mozwmmmko 0Zm30wwE PATENTEDHAR em 3.569.605

SHEET 2 BF 2 FIG. 3

"-TER m TABLET'JB DEVI CE FIG. 4

PLURAL CHANNEL TONE COLORING SYSTEM WITH COMMON MIXER FOR ELECTRONIC MUSICAL INSTRUMENT BACKGROUND OF THE INVENTION The present invention relates to the tone coloring system of an electronic musical instrument and more particularly to the tone coloring system of an electronic musical instrument which is capable of producing by key operation the tone colors of multiple reeds such as those derived from an accordion or harmonica.

An electronic musical instrument can give forth not only the tones of an ordinary organ but also a variety of tone colors resembling those of other musical instruments. To date, however, conventional electronic musical instruments have been unable to produce such tone colors aswill give the same impression as those of multiple reeds derived from, for example, an accordion or harmonica.

It is accordingly the object of the present invention to provide a tone coloring system of an electronic musical instrument which is capable of giving forth such musical tone colors as will have the same effect as those of multiple reeds obtained from, for example, an accordion or harmonica.

SUMMARY OF THE INVENTION The present invention is characterized by mixing a funda mental tone signal :emitted from a properly tuned first tone generating circuit having the tone colors derived from string voice or reed voice with a signal issued from a second tone generating circuit which has a frequency difference of 3 to Hz. as compared with the fundamental tone signal, a voltage corresponding to 3 to 6db. lower than those of said fundamental signal and is capable of producing the tone color of the like voice as represented by said fundamental tone signal, and using these mixed signals as the musical tone signals of an electronic musical instrument thereby easily to give forthby key operation musical tones having the desired types of tone colors. BRIEF EXPLANATION OF THE DRAWINGS FIG. I is a circuit diagram illustrating the principle of a tone coloring system according to the present invention;

FIGS. 2a and 2b represent the frequency relationship of two signals mixed by a circuit arranged as shown in FIG. 1;

FIG. 3 is a diagram of the circuit connection associated with a tone coloring system according to an embodiment of the invention; and

FIG. 4 is a concrete example of a connection used in a tone coloring circuit according to said embodiment.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, there is selectively derived an accurately tuned fundamental tone signal from the first tone generating circuit 11 through a keying circuit 12 which is actuated in accordance with the operation of the keys of an electronic musical instrument (not shown). The signal thus derived is supplied to a tone coloring circuit 13 used, if required. There is also provided a second tone generating circuit 14 to obtaina second signal having a frequency difference of- 3 to 10 Hz.

from the fundamental tone signal. Asignal from this second tone generating circuit 14 is selectively derived out through a second keying circuit 15 controlled in interlocking relationship with the first keying circuit -12, and supplied to a second tone coloring circuit 16 used when necessary.

In this case, the two signals from the two tone generating circuits 1] and 14 are only required to have a frequency difference of 3 to 10 Hz. therebetween. Thus, the signal from either of said circuits 11 and 14 may have a higher frequency than the other. The aforementioned frequency difference varies withthe frequency of signals from the tone generating circuits 11 and 14.

The tone coloring system of the present invention is so arranged to display as shown in FIG. 2a, a frequency difference of 3 Hz.in the neighborhood of the tone height of C 65.4 and 10 Hz. in the vicinity of C,: 2,093 Hz. FIG. 2b represents in percentage the relationship between the signal frequencies and differences therebetween.

The tone coloring circuits l3 and 16 which are supplied with signals from the keying circuits l2 and 15, respectively, each consist of, for example, an electric filter. The first tone coloring circuit 13 produces signals corresponding to a string voice or reed voice which are relatively rich with harmonics of odd and even order with respect to the fundamental tone signal, and the second tone coloring circuit 16 converts signals from the second tone generating circuit 14 to those having the like tone colors corresponding to a string or reed voice. In this case, the voltage of signals from the second tone coloring circuit 16 is set at a value corresponding to 3 to 6db. lower than that of signals from the first tone coloring circuit 13. Two signals having such characteristics are mixed in the mixing circuit 17 to obtain musical tones having the desired tone colors which will give the same impression as those of multiple reeds derived from, for example, an accordion or harmonica. The mixed tone signals are supplied toa speaker-operating circuit through an amplifier device 18, causing musical tones approximately corresponding to those of art-accordion or harmonica to be sounded.

There will now be described the present invention by reference to FIGS. 3 and 4. The tone generating circuit consists of a flip-flop circuit; 11a generating 8-foot-t0ne output signals of, for example, 440 Hz. Output signals from this circuit 11:: are conducted to the base region of a switching transistor 20 disposed in the keying circuit 12a. The emitter region of the transistor 20 is connected to a source of l2 volts through a resistor 2 having a relatively low value (3.2 kilohms) and condenser 22 connected in series. The junction between the resistor 21 and condenser 22 is connected to a source terminal of volts through a resistor 25 of 630'ohms and a resistor 26 of '50 kilohms connected in series. The base region of the transistor 20 is supplied with a bias voltage divided by a resistor 27 of 400 kilohms and a resistor 28 of 20 kilohms connected between the ground terminal and the l 2- volt source. A diode 30 whose cathode is connected to the junction between the resistors 25 and 26 and whose anode is connected to the variable terminal of the variable resistors 29 connected between the 9-volt source and the l2-volt source is used, as later described, as a circuit for charging a condenser 22 when the switch 24 is turned off.

Eight-foot tone generating signals from the keying circuit 12a are supplied to a first filter 43 included in the tone coloring circuit 13 to give forth the tone color of a string voice and a second filter 44 also enclosed therein to generate the tone color of a reed voice.

There are obtained four foot signals of 880 Hz. from a tone generating circuit llb consisting of a flip-flop circuit in addition to similar signals from the tone generating circuit 11a. The signals from the circuit 11b are supplied to the filters 43 and 44 through the keying circuit 12b having the same arrangement as the keying circuit 12a. A switch included in the circuit 12b is, of course, interlocked with the switch 24. The filters 43 and 44 have a circuit arrangement as shown in FIG. 4 and shape rectangular input signals into the waveforms adapted to produce the tone color of string and reed voices respectively. These filters 43 and 44 may consist of those generally used in the art, and a detailed description thereof is omitted.

The switch 24 is so arranged to operate in interlocking relationship with a switch 31 included in the keying circuit 15 provided in connection with the second tone generating circuit 14. One end of the switch 31 is connected to a source of +15 volts and the other end to the emitter region of a transistor 36 involved in the second tone generating circuit I4 through resistors 32 and 33, diode 34 and resistor 35. The tone generating circuit 14 constitutes a sine wave generator using the transistor 36 as an active element. The junction point between the resistor 33 and diode 34 is grounded through a diode .37 and switch 38. When the switch 38 is opened, the transistor 36 is supplied with a voltagefor oscillation. Whenthe switch is closed, the source voltage of volts is grounded through the diode 37 to stop the oscillation. Said generator is provided with a circuit for generating a sine wave signal having an oscillating frequency of 446.8 Hz. which is 6.8 Hz. higher than the 440 Hz. frequency of signals from the first tone generating circuit 11a.

The fundamental tone generator is comprised of a frequency dividing system using flip-flop circuits to cause all tone signals to be tuned to an exactly equal interval scale, so that said generator is incapable of adjusting individual tone signals separately.

On the other hand, the sine wave generator is an independent oscillator and well adapted to tune individual tone signals. Tuning is carried out by changing the value of elements involved in the tank circuit, for example, the inductance L as shown in FIG. 3.

Outputs of sine wave signals from the second tone generating circuit 14 are supplied to the succeeding tone coloring circuit 16, and are so shaped as to assume a waveform corresponding to the tone color of a string or reed voice. The tone coloring or shaping circuit 16 may consist of rectifiers and filters. Output signals from the tone coloring circuit 16 which give forth the tone color of a reed voice are conducted through a resistor 39 to one end of a switch 40, and those producing the tone color of a string voice are conducted through a condenser 41 to one end of a switch 42. The other end of each of the two switches 40 and 42 is connected to one end of the mixing circuit 17.

Outputs from the filters 43 and 44 are jointly supplied to the mixing circuit 17 through switches 45 and 46 to be mixed with outputs from the tone coloring circuit 16. In this case, outputs from the switches 45 and 46 are so arranged to have a voltage corresponding to 3 to 6db. higher than those from the tone coloring circuit 16. Needless to say, the signals supplied to the mixing circuit 17 should be so adjusted as to give the like tone color as that of a string or reed voice. For instance, when the switches 42 and 45 are closed, the signals are so mixed as to produce the tone color of a string voice, and when the switches 40 and 46 are closed they are so mixed to obtain the tone color of a reed voice. in either case, the musical tone signals fed out from the amplifier device 18 have tone colors approximating those of multiple reeds such as those derived from an accordion or harmonica.

The foregoing description relates to the case where tone signals having a pitch of 440 Hz. are treated. With respect to tone signals of other pitches, the frequency of the sine wave generator is so set as to conform to the relationship shown in FIGS. 2a and 2b. (The frequency deviation appears more prominent in the high frequency range than in the low frequency range, whereas the percentage deviation is larger in the low frequency range than in the high frequency range). The inventors experiments show that such a relationship proved to be the best condition for adjustment.

There will now be described the operation of the aforementioned embodiment. When the switch 24, and consequently a switch 31 and another switch (not shown) included in the keying circuit 12b, are closed in interlocking relationship with the keys of an electronic musical instrument, the charge stored in the condenser 22 of the keying circuit 12a is discharged through the resistor 23 with a prescribed time constant. This discharge causes the emitter potential of the transistor to be decreased with respect to the base potential thereof and the transistor 20 to be conducting. Thus rectangular 8-foot signals of 440 Hz. from the tone generating circuit 11a are supplied to the filters 43 and 44 of the tone coloring circuit 13 through the collector region of the transistor 20 and a condenser 47. Also rectangular 4-foot signals of 880 Hz. from the tone generating flip-flop circuit 11b having the same arrangement as the tone generating circuit lla are supplied to the filters 43 and 44 through the keying circuit 1211. At this time, the sine wave generator 14 is put into operation to generate a sine wave signal of 446.8 Hz. and supply it to the tone coloring circuit 16. Signals to give forth the tone color of a string or reed voice are selectively supplied from the switch 40 or 42 to the mixing circuit 17 so as to be mixed with the signals selectively derived out from the switch 45 or 46 which are intended to produce the tone color of the like voice. When the keys of an electronic musical instrument are brought back to the original positions, the switch 24 is opened and the condenser 22 is charged through a charging circuit consisting of the resistor 25, diode 30 and variable resistor 29..As the condenser 22 is charged, the transistor 20 is progressively turned off with the increasing emitter region potential thereof. The speed at which the transistor 20 is turned off isproportional to that at which the emitter potential rises, so that said turnoff speed can be controlled by the time constant at which the charging circuit consisting of the resistor 25, diode 30 and variable resistor 29 is operated, as well as by varying the resistance of the variable resistor 29.

When the switch 38 is closed to make its contact, the sine wave oscillator 14 is rendered inoperable, causing no occurrence of ordinary humming, but giving forth musical tones corresponding to those derived from reed or string instruments.

According to the foregoing embodiment, tone generating signals having a rectangular or sine wave are converted by a tone coloring circuit to those capable of producing the tone color of a string or reed voice. It will be apparent that if signals capable of giving forth the tone color of a string or reed voice are initially used as tone generating signals then the tone coloring circuit will be unnecessary.

1. A tone coloring system of an electronic musical instrument comprising:

a source of a fundamental tone signal having a tone color corresponding to that derived from a string voice or reed voice;

a source of a second signal having a frequency difference of 3 to 10 Hz. as compared with said fundamental tone signal, a voltage corresponding to 3 to 6db. lower than that of said fundamental tone signal and which is capable of producing the tone color of the like voice as represented by said fundamental tone signal; and

means for mixing said fundamental and second signals to obtain musical signals having tone colors approximately corresponding to those of multiple reeds.

2. A system according to claim 1 wherein said source of a fundamental tone signal includes an accurately tuned tone generating circuit.

3. A system according to claim 1 wherein said source of a fundamental tone signal includes flip-flop tone generating circuit providing rectangular wave signals; a keying circuit coupled to said tone generating circuit for selecting fundamental signals of desired frequencies; and a filter coupled to said keying circuit to filter said rectangular wave signals provided by said flip-flop tone generating and keying circuits.

4. A system according to claim 1 wherein said source of a second tone signal includes a sine wave generator and a tone coloring circuit coupled to the output of said sine wave generator.

5. A system according to claim 4 wherein said tone coloring circuit includes at least one rectifier coupled to a filter.

6. A method for generating musical signals having tone colors approximately corresponding to those of multiple reeds comprising the steps of:

generating a fundamental tone signal having a tone color corresponding to that derived from'a string voice or reed voice;

generating a second signal having a frequency difference of 3 to 10 Hz. as compared with said fundamental tone signal, a voltage corresponding to 3 to 6db. lower than that of said fundamental tone signal and which is capable of producing the tone color of the like voice as represented by said fundamental tone signal; and

mixing said fundamental and second signals to obtain musical signals having tone colors approximately corresponding to those of multiple reeds. 

1. A tone coloring system of an electronic musical instrument comprising: a source of a fundamental tone signal having a tone color corresponding to that derived from a string voice or reEd voice; a source of a second signal having a frequency difference of 3 to 10 Hz. as compared with said fundamental tone signal, a voltage corresponding to 3 to 6db. lower than that of said fundamental tone signal and which is capable of producing the tone color of the like voice as represented by said fundamental tone signal; and means for mixing said fundamental and second signals to obtain musical signals having tone colors approximately corresponding to those of multiple reeds.
 2. A system according to claim 1 wherein said source of a fundamental tone signal includes an accurately tuned tone generating circuit.
 3. A system according to claim 1 wherein said source of a fundamental tone signal includes flip-flop tone generating circuit providing rectangular wave signals; a keying circuit coupled to said tone generating circuit for selecting fundamental signals of desired frequencies; and a filter coupled to said keying circuit to filter said rectangular wave signals provided by said flip-flop tone generating and keying circuits.
 4. A system according to claim 1 wherein said source of a second tone signal includes a sine wave generator and a tone coloring circuit coupled to the output of said sine wave generator.
 5. A system according to claim 4 wherein said tone coloring circuit includes at least one rectifier coupled to a filter.
 6. A method for generating musical signals having tone colors approximately corresponding to those of multiple reeds comprising the steps of: generating a fundamental tone signal having a tone color corresponding to that derived from a string voice or reed voice; generating a second signal having a frequency difference of 3 to 10 Hz. as compared with said fundamental tone signal, a voltage corresponding to 3 to 6db. lower than that of said fundamental tone signal and which is capable of producing the tone color of the like voice as represented by said fundamental tone signal; and mixing said fundamental and second signals to obtain musical signals having tone colors approximately corresponding to those of multiple reeds. 